Modern mobile telecommunications standards continue to demand increasingly greater rates of data exchange (data rates). One way to increase the data rate of a wireless communications device is through the use of carrier aggregation. Carrier aggregation allows a single wireless communications device to aggregate bandwidth across one or more operating bands in the wireless spectrum. The increased bandwidth achieved as a result of carrier aggregation allows a wireless communications device to obtain higher data rates than have previously been available.
FIGS. 1A and 1B show tables describing a number of wireless communication operating bands in the wireless spectrum. Specifically, FIG. 1A shows a table describing a number of frequency division duplexing (FDD) operating bands, while FIG. 1B shows a table describing a number of time division duplexing (TDD) operating bands as defined by Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) standards. The first column in FIGS. 1A and 1B indicates the operating band number for each one of the operating bands. The second column in FIGS. 1A and 1B indicate the uplink frequency band for each one of the operating bands. The third column in FIG. 1A indicates the downlink frequency band for each one of the operating bands. Since the operating bands shown in FIG. 1B are TDD operating bands, the uplink and downlink frequency bands are the same. In non-carrier aggregation configurations, a wireless communications device will generally communicate using a single portion of the uplink or downlink frequency bands within a single operating band. In carrier aggregation applications, however, a wireless communications device may aggregate bandwidth across a single operating band or multiple operating bands in order to increase the data rate of the device.
FIG. 2A shows a diagram representing a conventional, non-carrier aggregation configuration for a wireless communications device. In this conventional configuration, a wireless communications device communicates using a single portion of the wireless spectrum 10 within a single operating band 12. Under the conventional approach, the data rate of the wireless communications device is constrained by the limited available bandwidth.
FIGS. 2B-2D show diagrams representing a variety of carrier aggregation configurations for a wireless communications device. FIG. 2B shows an example of contiguous intra-band carrier aggregation, in which the aggregated portions of the wireless spectrum 14A and 14B are located directly adjacent to one another and are in the same operating band 16. FIG. 2C shows an example of non-contiguous intra-band carrier aggregation, in which the aggregated portions of the wireless spectrum 18A and 18B are located within the same operating band 20, but are not directly adjacent to one another. Finally, FIG. 2D shows an example of inter-band carrier aggregation, in which the aggregated portions of the wireless spectrum 22A and 22B are located in different operating bands 24 and 26. A modern wireless communications device should be capable of supporting each one of the previously described carrier aggregation configurations.
The various carrier aggregation configurations discussed above can be performed between two or more FDD operating bands, two or more TDD operating bands, or a combination thereof. Generally, a wireless communications device will aggregate bandwidth when receiving data (i.e., during downlink), but will use a single operating band when transmitting data (i.e., during uplink). However, carrier aggregation may also be used during data transfer to increase uplink throughput.
FIG. 3 shows a schematic representation of conventional radio frequency (RF) front end circuitry 28 configured to support at least one carrier aggregation configuration. The conventional RF front end circuitry 28 includes a first antenna 30A, a second antenna 30B, antenna switching circuitry 32 coupled to the first antenna 30A and the second antenna 30B, RF filtering circuitry 34 coupled between the antenna switching circuitry 32 and a number of input/output nodes 36 (shown individually as 36A through 36K), and transceiver circuitry 38 coupled to the input/output nodes 36. The RF filtering circuitry 34 includes a number of filters 40 (shown individually as 40A through 40K), which are grouped into first multiplexer circuitry 42A and second multiplexer circuitry 42B. Specifically, a number of the filters 40 configured to support one or more FDD operating bands are grouped into the first multiplexer 42A and the second multiplexer 42B, while a number of the filters 40 configured to support one or more TDD operating bands are provided individually and thus are isolated from the other filters 40. A first diplexer 44A and a second diplexer 44B separate FDD signals from TDD signals as discussed in detail below.
The first multiplexer 42A includes a first filter 40A coupled between a first common node 46 and a first input/output node 36A, a second filter 40B coupled between the first common node 46 and a second input/output node 36B, a third filter 40C coupled between the first common node 46 and a third input/output node 36C, a fourth filter 40D coupled between the first common node 46 and a fourth input/output node 36D, a fifth filter 40E coupled between the first common node 46 and a fifth input/output node 36E, and a sixth filter 40F coupled between the first common node 46 and a sixth input/output node 36F.
A seventh filter 40G is coupled between a first isolated filter node 48 and a seventh input/output node 36G.
An eighth filter 40H is coupled between a second isolated filter node 50 and an eighth input/output node 36H.
The second multiplexer 42B includes a ninth filter 40I coupled between a second common node 52 and a ninth input/output node 36I, a tenth filter 40J coupled between the second common node 52 and a tenth input/output node 36J, and an eleventh filter 40K coupled between the second common node 52 and an eleventh input/output node 36K.
The RF filtering circuitry 34 is configured to selectively pass RF transmit signals and RF receive signals within a first operating band (band A), a second operating band (band B), a third operating band (band C), and a fourth operating band (band D) between the antenna switching circuitry 32 and the transceiver circuitry 38, where the first operating band (band A), the second operating band (band B), and the third operating band (band C) are FDD operating bands, and the fourth operating band (band D) is a TDD operating band. As discussed below, the RF filtering circuitry 34 facilitates at least one carrier aggregation configuration in the conventional RF front end circuitry 28.
The filter response of each one of the filters 40 includes a pass band configured to pass RF signals within a particular frequency range, while attenuating other signals. Specifically, the pass band of each one of the filters 40 is designed to pass only those signals within a transmit or receive frequency band of a particular operating band (or multiple operating bands), such as the transmit and receive frequency bands shown above for each operating band in FIG. 1.
As shown in FIG. 3, a filter response of the first filter 40A includes a pass band configured to pass RF transmit signals within the first operating band (band A) while attenuating other signals. A filter response of the second filter 40B includes a pass band configured to pass RF receive signals within the first operating band (band A) while attenuating other signals. A filter response of the third filter 40C includes a pass band configured to pass RF transmit signals within the second operating band (band B) while attenuating other signals. A filter response of the fourth filter 40D includes a pass band configured to pass RF receive signals within the second operating band (band B) while attenuating other signals. A filter response of the fifth filter 40E includes a pass band configured to pass RF transmit signals within the third operating band (band C) while attenuating other signals. A filter response of the sixth filter 40F includes a pass band configured to pass RF receive signals within the third operating band (band C) while attenuating other signals.
A filter response of the seventh filter 40G includes a pass band configured to pass RF transmit signals and RF receive signals within the fourth operating band (band D) while attenuating other signals. Because the fourth operating band (band D) is a TDD band where RF transmit signals and RF receive signals are in the same frequency band, a transmit/receive switch 54 is coupled between the seventh filter 40G and the transceiver circuitry 38 to switch the output of the seventh filter 40G between separate transmit and receive signal paths in the transceiver circuitry 38. A filter response of the eighth filter 40H includes a pass band configured to pass RF receive signals within the fourth operating band (band D) while attenuating other signals. As discussed in detail below, since the eighth filter 40H is used only for receiving diversity multiple-input-multiple-output (MIMO) signals and thus does not need a transmit/receive switch.
A filter response of the ninth filter 40I includes a pass band configured to pass RF receive signals within the first operating band (band A) while attenuating other signals. A filter response of the tenth filter 40J includes a pass band configured to pass RF receive signals within the second operating band (band B) while attenuating other signals. A filter response of the eleventh filter 40K includes a pass band configured to pass RF receive signals within the third operating band (band C) while attenuating other signals.
The conventional RF front end circuitry 28 is capable of operating in a standard (i.e., non-carrier aggregation) mode in any one of the first operating band (band A), the second operating band (band B), the third operating band (band C), and the fourth operating band (band D). During standard modes, a first one of the antennas 30 is used to transmit and receive primary signals within a single operating band, while a second one of the antennas 30 is used to receive a diversity MIMO signal within the same operating band. Generally, the first multiplexer 42A and the seventh filter 40G are used for the primary transmission and reception of RF signals for the various operating bands, while the second multiplexer 42B and the eighth filter 40H are used for the reception of diversity or MIMO receive signals. The particular one of the antennas 30 used for transmission may be changed based on one or more performance characteristics of each one of the antennas 30 (e.g., voltage standing wave ratio), and may be dynamically swapped by the antenna switching circuitry 32 in order to optimize transmission and/or reception. In particular, switch control circuitry 56 coupled to the antenna switching circuitry 32 may provide control signals to the antenna switching circuitry 32 in order to swap the first antenna 30A and the second antenna 30B.
The conventional RF front end circuitry 28 is further configured to operate in several carrier aggregation configurations in which bandwidth between the first operating band (band A), the second operating band (band B), the third operating band (band C), and the fourth operating band (band D) is aggregated. In the various carrier aggregation modes of the conventional RF front end circuitry 28, an RF transmit signal in one of the operating bands is provided to either the first RF multiplexer circuitry 42A or the seventh filter 40G, where it is passed by the first diplexer 44A to one of the antennas 30 via the antenna switching circuitry 34. RF receive signals in two or more of the operating bands are received at both the first antenna 30A and the second antenna 30B and separately delivered to the transceiver circuitry 38 by the RF filtering circuitry 34. As discussed above, the first RF multiplexer circuitry 42A and the seventh filter 42G are generally used for the reception of primary signals, while the second RF multiplexer circuitry 42B and the eighth filter 42H are generally used for the reception of diversity or MIMO signals. Because the first operating band (band A), the second operating band (band B), and the third operating band (band C) are FDD operating bands, while the fourth operating band (band D) is a TDD operating band, there may be a relatively large frequency delta between these signals (as TDD operating bands are sometimes significantly higher in frequency than FDD operating bands). As will be appreciated by those skilled in the art, the larger the separation between pass bands in various filters, the more loading they generally present to one another. Accordingly, the first diplexer 44A and the second diplexer 44B are provided to isolate the first RF multiplexer circuitry 42A from the seventh filter 40G and the second RF multiplexer 42B from the eighth filter 40H, respectively.
While the conventional RF multiplexer circuitry 28 is capable of operating in carrier aggregation configurations using the first operating band (band A), the second operating band (band B), the third operating band (band C), and the fourth operating band (band D), the first diplexer 44A and the second diplexer 44B may significantly degrade the performance of the circuitry. Specifically, the first diplexer 44A and the second diplexer 44B may add significant insertion loss in the transmit and receive paths of the antennas 30. Accordingly, there is a need for RF front end circuitry capable of supporting carrier aggregation between FDD operating bands and TDD operating bands with improved performance.